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SWMU Building 43 RCRA Facility Investigation Report

Section 1 - Introduction

On May 5, 1999, an Administrative Consent Order was issued to Camp Stanley Storage Activity (CSSA) pursuant to 3008(h) of the Safe Drinking Water Act (SDWA), as amended by the Resource Conservation and Recovery Act (RCRA), and further amended by the Hazardous and Solid Waste Act (HSWA) of 1984.In accordance with the RCRA Facility Investigation (RFI) requirements of the Consent Order, this report has been prepared to document the environmental condition and site closure requirements of Solid Waste Management Unit (SWMU) Building 43 and to recommend further investigation, if necessary, or to provide documentation necessary for site closure.The main objectives of the SWMU Building 43 investigation are to determine if the site meets Texas Commission on Environmental Quality (TCEQ) requirements for closure, as described in Section 1.4, and to meet requirements of the Consent Order.

This specific RFI was performed by Parsons ES under the U.S. Air Force AMC Contract F11623-94-D-0024, delivery orders (DOs) RL17 and RL53. AFCEE provided technical oversight for the DO. Based upon the project Statement of Work (SOW), a set of work plans was established to govern the fieldwork.  These include:

Work Plan Overview

(Volume 1-1, RL17 and RL53 Addendum);

Site-Specific Work Plan

(Volume 1-2, Building 43);

Field Sampling Plan

(Volume 1-4, RL17 and RL53 Addendum); and

Health and Safety Plan

(Volume 1-5, RL17 and RL53 Addendum).

For this RFI report, Section 1 provides the site-specific background and closure standard. Section 2 describes field actions and closure evaluations.  Section 3 summarizes the findings, evaluates attainment of data quality objectives (DQOs), provides recommendations and certifies the site closure, if applicable.  References cited in this report can be found in the Bibliography (Volume 1-1 of the Environmental Encyclopedia).

1.1 - Background and Site Description

1.1.1   CSSA

General information regarding the history and environmental setting of CSSA is provided in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report).In that report, data regarding the geology, hydrology, and physiography are also available for reference.

1.1.2   SWMU Building 43

1.1.2.1   Site Description

SWMU Building 43 was previously used as a makeshift ammunition demolition facility.The site includes a small building and the surrounding area.The building is a three-walled structure made of cinder blocks.A small brick and steel burn area is located at the back of the building.The building dimensions are approximately 10 feet by 10 feet.Miscellaneous solid waste and ammunition were burned inside the burn box.Metal debris, fuses, shotgun shells, and casings are scattered across the ground surface of the site. Large sections of the site are covered in molten conglomerations of bomb fuses, bullets, spent casings, and other unidentified metal pieces.One large section of debris leads away from the back of the building towards the western edge of the site.Another section was located near the trees at the northern edge of the site. Additional scattered metal pieces surround the building.Background information regarding the location, size, and known historical use of SWMU Building 43 is also included in the Environmental Encyclopedia (Volume 1-2, Building 43).Volume 1-2 includes a Chronology of Actions and a Site Specific Work Plan for SWMU Building 43.

1.1.2.2 Potential Sources of Contamination

SWMU Building 43 was used as a makeshift ammunition demolition facility to burn miscellaneous solid waste and ammunition.The area adjacent to Building 43 is covered with molten metal debris and spent ammunition. Because of its use as a demolition facility, the potential constituents of concern are volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), metals, explosives, dioxins, and furans.

1.1.2.3   Site Location

SWMU Building 43 is located in the northeast corner of the inner cantonment, approximately 800 feet from the western edge of CSSA (Figure BLDG43-1), beside a dirt road. SWMU B-10 is 25 feet to the west.SWMU B-19 and Area of Concern (AOC)-36 are approximately 140 feet to the west, SWMU Oxidation Pond (O-1) is approximately 240 feet to the south, SWMU B-28 is approximately 270 feet to the west, and SWMU B-3 is approximately 375 feet to the north-northwest.

1.2 - Environmental Setting

1.2.1   Site Soils and Topography

The soils at SWMU Building 43 are Tarrant Association, gently undulating (Figure Building 43-2). The gently undulating Tarrant Association soils comprise approximately 14.3 percent of CSSA and are typical of prairie and plateau topography. They occur in areas that do not have streams, such as the north-central area of the north cantonment, and are found on Steele and Wells Hills, and other hills located north of the inner cantonment. Generally, Tarrant Association, gently undulating soils are dark colored, very shallow, calcareous, and clayey. They are best suited for native grasses and range use.  At SWMU Building 43, the gently undulating Tarrant Association soils are from 3 to 10 feet thick. Detailed descriptions of all the CSSA soil types are provided in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology).

The ground surface at SWMU Building 43 slopes to the west-southwest toward Salado Creek, and the site is situated at an elevation of approximately 1,240 feet above sea level. There are no changes in topography in the immediate vicinity of SWMU Building 43, and no ditches or trenches or intermittent streambeds are in the immediate vicinity of SWMU Building 43. Salado Creek flows southward and is located approximately 600 feet southwest from SWMU Building 43.

1.2.2   Site Geology

The Upper Glen Rose Formation is the uppermost geologic stratum in the area of SWMU Building 43 (Figure Building 43-3).The Upper Glen Rose Formation consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds.Generally, it outcrops in stream valleys and at the ground surface.The thickness of the Upper Glen Rose Formation is estimated to be between 20 and 150 feet at CSSA.It is underlain by the Lower Glen Rose, which is estimated to be 300 feet thick at CSSA. The Lower Glen Rose is a massive, fossiliferous, and vuggy limestone that grades upwards into thin beds of limestone, marl, and shale.The Lower Glen Rose is underlain by the Bexar Shale (regionally known as the Hensell Shale), which is from 80 to 150 feet thick at CSSA.The Bexar Shale consists of silty dolomite, marl, calcareous shale, and shaley limestone.The geologic strata dip approximately 10 to 12 degrees to the south-southeast at CSSA.

Based on current published information, there are two known major fault (shatter) zones at CSSA: the North Fault Zone and the South Fault Zone. SWMU Building 43 is located within the North Fault Zone, between a series of faults trending northeast/southwest (Figure Building 43-3). At SWMU Building 43, soil boring logs recorded in February and March 2000 (Appendix B) indicate limestone was encountered at a depth of 4 to 10 feet below ground surface (bgs).

1.2.3   Hydrology

At CSSA, the uppermost hydrogeologic layer is the unconfined Upper Trinity aquifer, which consists of the Upper Glen Rose Limestone. Locally at CSSA, low-yielding perched zones of groundwater can exist in the Upper Glen Rose. Transmissivity values are not available for the Upper Glen Rose. Regionally, groundwater flow is thought to be enhanced along the bedding contacts between marl and limestone; however, the hydraulic conductivity between beds is thought to be poor. This interpretation is based on the observation of discordant static water levels in adjacent wells, completed in different beds.  Principle development of solution channels is limited to evaporite layers in the Upper Glen Rose Limestone.

The Middle Trinity aquifer is unconfined and functions as the primary source of groundwater at CSSA. It consists of the Lower Glen Rose Limestone, the Bexar Shale, and the Cow Creek Limestone. The Lower Glen Rose Limestone outcrops north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, principle recharge into the Middle Trinity aquifer is via precipitation infiltration at outcrops. At CSSA, the Bexar Shale is interpreted as a confining layer, except where it is fractured and faulted, allowing vertical flow from the up-dip Cow Creek Limestone into the overlying, but down-dip Lower Glen Rose. Fractures and faults within the Bexar Shale may allow hydraulic communication between the Lower Glen Rose and Cow Creek Limestones. Groundwater flow within the Middle Trinity aquifer is toward the south and southeast and the average transmissivity coefficient is 1,700 gallons per day per feet (gpd/ft) (Ashworth, 1983).  In general, groundwater at CSSA flows in a northeast to southwest direction.  However, local flow gradient may vary depending on rainfall, recharge, and possibly well pumping.

SWMU Building 43 is located within the North (Shatter) Fault Zone, which extends the central portion of CSSA in a northeast-southeast direction.The fault zones and/or fracture systems associated with the fault zones may be the controlling structural feature for migration of contaminants in the vadose zone at CSSA (Volume 1-1, Background Information Report, Groundwater Resources).

No site-specific information regarding groundwater is available.However, the nearest well, Well CS-16, is approximately 500 feet north of SWMU Building 43 and Well CS-D is located approximately 700 feet northwest of SWMU Building 43.Between 1992 and 2001, water levels in Well CS-16 have ranged from between approximately 78 feet bgs (November 1998) and 317 feet bgs (April 1995) (Environmental Encyclopedia, Volume 5).

The nearest surface water is Salado Creek, which is approximately 250 feet west of SWMU Building 43.Salado Creek is an intermittent stream that flows to the south, and exits the southeast portion of CSSA.

1.2.4   Cultural Resources

Cultural resources are prehistoric and historic sites, structures, districts, artifacts, or any other physical evidence of human activity considered important to a culture, subculture, or community for scientific, traditional, or religious purposes. Building 43 is a historic building.

1.2.5   Potential Receptors

A land use survey discussing local and possible future uses of groundwater and surface water, a water well survey, and sensitive environmental areas at CSSA was completed on December 15 and 16, 1999.The results of this survey, along with results from a more in-depth survey to identify potential receptors, points of human exposure, and possible constituent pathways is presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1-6).

A small herd of cattle is maintained on CSSA by the USDA-ARC.The cattle roam freely throughout the Inner Cantonment and in selected areas of the North Pasture.CSSA also manages wild game species for the purpose of hunting.White-tailed deer, axis deer, and wild turkey all roam freely throughout CSSA.A map of deer hunting stands which overlook mechanical feeders and planted food plots is located in the Technical Approach Document for Risk Evaluation (Volume 1-6).SWMU Building 43 is located approximately 400 feet south of hunting stand number 2 and 1,500 feet north of hunting stand number 3.Four water tanks are maintained at CSSA for the purpose of sport fishing.Two of the tanks are located in the northwestern and northeastern portions of the North Pasture while the other two tanks are located near the western boundary of the Inner Cantonment.

There are no residential use properties adjacent to SWMU Building 43.Generally, CSSA is a controlled access facility with access limited by both a security guard and a perimeter fence.Wildlife such as deer and turkey may use the area surrounding SWMU Building 43.Potential habitat for the golden-cheeked warbler and black-capped vireo, which are both endangered species, is located along the divide between the inner cantonment and the East Pasture, which is less than 1,000 feet to the east of SWMU Building 43.The area around the building is partially covered with grasses, with exposed soils covering the rest of the site.The closest drinking water well (RFR-3) is located off-post, approximately 5,000 feet west-northwest of SWMU Building 43.

1.3 - Previous Investigations

On July 19, 1995, a soil gas survey was performed at SWMU B-3, SWMU B-4, and in the area between these two SWMUs.SWMUs B-3 and B-4 are approximately 750 feet apart, SWMU Building 43 lies between the two sites. The survey grid was set for data collection every 100 feet in the area between B-3 and B-4.The highest tetrachloroethene (PCE) concentration detected in this area was 6.1 micrograms per liter (g/L) and occurred at a location approximately 275 feet north of SWMU Building 43 (100 feet south of B-3).Results for the other points between SWMUs B-3 and B-4 are provided in Table 9.1 of the Technical Memorandum on Soil Gas Surveys (Parsons ES, 1995b).

Based on the results of the July 1995 survey, an additional survey of the area between SWMU B-3 and the O-1 was conducted in November and December 1995.Soil gas at 24 additional points between these two SWMUs were sampled and analyzed for cis‑1,2‑DCE, PCE, trichloroethene (TCE), and carbon tetrachloride.The closest samples to SWMU Building 43 included locations G,13; G,14; G,15; I,13; I,15; I,16; and J,16 which are shown on Figure Building 43-4.PCE was the only analyte detected in soil gas at these locations, and concentrations ranged from 0.05 μg/L to 0.43 μg/L.The highest concentration, 0.43 μg/L, was detected at location I,16; which is located approximately 75 feet south of the area designated as SWMU Building 43.Results from the November/December 1995 soil gas survey are included in Table Building 43-1.

1.4 - Closure Standard

As described in Section 4.3 of the Risk Assessment Technical Approach Document (Volume 1-6), CSSA has opted to pursue closure of SWMU Building 43 under the Risk Reduction Rule (RRR) (30 Texas Administrative Code [TAC] 335).If the site concentrations do not exceed background, then the site will be closed using RRS1.If the site exceeds background, then a determination will be made regarding the feasibility of cleaning the site to meet background concentrations.If the decision is made to clean the site to background, closure under RRS1 will be sought.However, if it is determined that the site cannot be closed to meet background concentrations, then the site will be closed under Texas Risk Reduction Program (TRRP).A notification of intent to close sites identified to date (including SWMU Building 43) in accordance with the former RRR was sent to the TCEQ on July 12, 1999. TCEQ acceptance of this notification was received on October 5, 1999.

RRS1 requires that the site be closed following removal or decontamination of waste, waste residues, and contaminated operation system components; and demonstration of attainment of cleanup levels (30 TAC 335.554).If closure requirements under RRS1 are attained and approved by the TCEQ Executive Director, then the owner is released from deed recordation requirement.

Since the chemical of concerns (COCs) for SWMU Building 43 are VOCs, SVOCs, metals, explosives, dioxins and furans, the cleanup levels should be the reporting limits (RLs) for VOCs, SVOCs, explosives, dioxins and furans and the soil or rock background values for metals. Background metals levels were statistically calculated for CSSA soils and the Glen Rose Limestone, and are reported in the Second Revision to the Evaluation of Background Metals Concentrations in Soil Types (Parsons ES, February 2002). TCEQ approved the background metals concentrations on April 23, 2002.

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